Differential Lockers & CDL

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Apr 29, 2008
South Kansas City, MO
I've done a TON of reading on here to try and determine why my lockers wont kick in. However, I haven't been able to find my exact situation so here goes....

My 97 has factory locks that only flash and never lock in..I've done the CDL lock test by going to a gravel area and putting it in low and doing the figure 8's and circles. I'm convinced the CDL is locking because of the amount of tire slippage. However, I dont get any light or any indication that I'm in 4-low or ABS or anything.

Can someone please tell me if there is a light that is supposed to illuminate when you're in 4-low? and when the CDL is locked?

I think that my problem is probably that my lockers dont know the CDL is engaged..(I'm hoping)

Thanks for the help.:)
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When the CDL is locked, the CDL light on the dash will come on.

Is the CDL light coming on?
NO....no light at all of any kind. My cruiser doesnt have a CDL button though.
I see.

When you put it in Low range, the CDL *should* automatically lock, which will kick off the ABS. This will turn on both the CDL and ABS lights. However, the CDL light will not come on until the CDL is engaged, and THAT is when the F/R lockers will be able to engage.

The CDL is probably still sticky. Keep at those figure-8s until that light pops on.
You could also crawl under the truck and have a buddy lock the CDL (put it into Low Range) while you listen for the CDL actuator.
Are you certain that a 97 cruiser has this CDL and ABS lights? 2nd question, can you see these lights on your cluster when you turn the key all the way forward without starting the vehicle??
Are you certain that a 97 cruiser has this CDL and ABS lights? 2nd question, can you see these lights on your cluster when you turn the key all the way forward without starting the vehicle??

Absolutely 100% positive that it has the lights.

I know the CDL won't show up when the key is initially turned, but I'm not sure about the ABS light. I don't have ABS...
OK, well that helps. Thank you.

I guess I'm thinking that if the activation sensor is not working then the rest of the stuff wouldnt know it was activated and therefore not engage. I've read about jumpering the activation sensor with a paperclip....I think I'll give that a go.
The ABS light and f&r diff lock lights should light up when you turn the ignition on. The CDL light does not.

You'd probably notice other stuff not working, but have you checked for a blown fuse?
The ABS light will come on when you turn the key to ON.

I would try shifting the transfer from high to low repeatedly. Like 50 times repeatedly. Some of the contacts in the system (not sure which ones/where) may be gunked up from lack of use; shifting a lot should clean them off. Good luck!
Your CDL is locking, it just doesn't know it's locking. There is a sensor/switch on the t-case that tells the diff lock ecu that the t-case is locked. It's easy to pull out and all it takes is to push the contact ball in a bunch of times to get it working. It just hasn't been used enough in a long time.
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Now we're talking

Thanks Bear80 That exactly the info I was looking for....:bounce:

Thanks all for input
I have a 96,when I shift in 4low the cdl and the abs ligt up.You can feel the high torque and ready to craw.In your case,I think it could be the bulbs in your instrument panel or the fuse.If you can feel the high torque and want to craws.Hope this help.:D
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Not sure how much experience you have with 4wds, but does it feel like its locked when you shift into low and turn? Can you feel the tires breaking loose?
Walleye, I've got the same problem from not driving it for a while, even with the cdl switch and 7 pin mod. I'd follow bear's advice, then possibly look into a bad light or fuse.
I have been down this road, as a matter of fact, I am still on that road, and I still haven't cracked the code.

I shifted the transfer case back and fourth 50-75 times - that didn't work.

Drove figure 8s until I got vertigo - that didn't work.

Bought and installed a new transfer case switch from CDan - that didn't work.

I grounded the connection at the CDL switch and -That worked, ie both the ABS and CDL light illuminated. - I don't know what to do at this point, it may time to take it to the dealership and let them figure out. I don't want to go down that road, but I'm running out of options. Is my center diff fried?

I'm going to rip that sensor out tonight and see if I can get it unstuck? Is it OK to use pb-blaster on it?
Therer's no need for pb-blaster. You'll see how the switch works when you get it out. Simply press it on the work bench to push the ball in and do this at a rapid pace several times. Then check it with a multimeter to ensure it's working again. If this doesn't do it, a new one will be needed.

campoj2- The diff lock is a very simple system and your problem seems to be that the diff is NOT locking. The new switch you bought has nothing to do with this function, only to tell the diff lock ecu that the diff locked/unlocked. ToolsRus had a similar problem that turned out to be a broken wire near the locker motor. This sounds to be an area for you to check.
Found the sensor...pulled the wire and jumpered it and Presto! ABS & Diff-Lock lights on. I have not tried lockers yet as I want to get sensor working first. OK, so now the question;

How the heck do you get a wrench on that sensor? It's like a 1 1/16 bolt....I couldnt get anything up there to get it loose.

Thanks for the help.

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